1. Field of the Invention
The present invention relates to a process for the treatment of a slag generated in a blast furnace, converter or electric furnace of an ironworks. Particularly, it relates to a dry process for the treatment of a slag generated in an ironworks.
2. Description of the Prior Art
Up to this time, a slag generated in an ironworks has been used in reclamation after the selective recovery of a big ingot by hands or has been discarded as such. However, such a slag still contains metals as shown in Table 1, even after the above selective recovery. Therefore, the recovery of such remaining metals has been carried out.
In this specification, the term "metal" refers to one having a particle size of 0.5 mm or above contained in a slag.
TABLE 1 ______________________________________ (weight %) metal content rate ______________________________________ stainless steel slag 1.5.about.2.5 common steel slag 2.about.3 special steel slag 0.5.about.1.5 ______________________________________
For example, a slag generated in an ironworks, particularly, a stainless steel slag generated in a stainless steel-manufacturing step, has been treated by a process which comprises crushing a solidified slag into a proper particle size and passing the crushed slag through a gravity separater to thereby recover metals having high specific gravities.
The above process has been generally carried out by using a wet jig wherein the crushed stainless steel slag is thrown into flowing water to be divided into heavy metals and a light slag based on the difference in specific gravity. Therefore, the process has a disadvantage in that such a jig cannot be used in winter, because water freezes in that season.
Further, when a stainless steel slag is passed through a wet separator to thereby recover metals, the residual slag forms sludge and therefore must be suitably dried to be used as a resource such as filler material. That is to say, the process has another disadvantage in that the residual slag requires additional treatments.
On the other hand, although a process which comprises recovering metals from a crushed stainless steel slag having a proper particle size with a dry magnetic separator has been sometimes carried out, it has a disadvantage in that an austenitic stainless steel can not effectively be recovered from a slag containing it, because an austenitic stainless steel is not adherent to a magnet.
Although these disadvantages have been described with respect to a stainless steel slag, similar disadvantages occur when a common steel slag or a special steel slag is treated by a wet process.